Imaging device and image sensor

ABSTRACT

An imaging device is described which, in some examples, includes general pixels and phase difference pixels. The general pixels, when operated by control signals, receive light from a subject and generate currents or voltages that are measured; a depth is estimated based on the measurements. The phase difference pixels generate currents based on a switched charge source. Data obtained from the currents generated by the phase difference pixels is used to adjust the control signals and thereby improve an accuracy of the depth estimation.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit of priority to Korean Patent ApplicationNo. 10-2019-0034179 filed on Mar. 26, 2019 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

The present application relates to an imaging device and an imagesensor.

An image sensor is a semiconductor-based sensor receiving light toproduce an electrical signal, which may include a pixel array having aplurality of pixels, a logic circuit for driving the pixel array andgenerating an image, and the like. In recent years, in addition to aconventional image sensor, research on an imaging device in which alight source for outputting an optical signal of a specific wavelengthband is combined with an image sensor has been actively studied.

SUMMARY

An aspect of the present application is to improve performance of animaging device generating a depth map using a phase difference between areceived optical signal and an output optical signal.

According to an aspect of the present application, an imaging deviceincludes: a light source operated by a light control signal; and a pixelarray including a plurality of pixels, each of the plurality of pixelsincluding a pixel circuit generating an electrical signal based on anelectric charge, wherein general pixels among the plurality of pixelscomprise a photodiode generating the electric charge in response to areceived optical signal output from the light source and reflected by asubject, and phase difference detection pixels among the plurality ofpixels comprise an electric charge-supplying source outputting theelectric charge, and a switch element being turned on and turned off bya switch control signal to supply the electric charge to the pixelcircuit.

According to an aspect of the present application, an image sensorincludes: a pixel array including a plurality of pixels, at least aportion of the plurality of pixels including a first pixel circuithaving a first photogate connected to a pixel node, a second pixelcircuit having a second photogate connected to the pixel node, a switchelement connected to the pixel node, and an electric charge-supplyingsource connected to the switch element; and a controller configured toinput a first photo-control signal to the first photogate, input asecond photo-control signal having a phase difference of 180 degreesfrom the first photo-control signal to the second photogate, and turn onand turn off the switch element to supply an electric charge to thepixel node.

According to an aspect of the present application, an image sensorincludes: a pixel array including first pixels disposed along a firstphoto-control line, and second pixels disposed along a secondphoto-control line, each of the first pixels and the second pixelsincluding a photodiode generating an electric charge, and a pixelcircuit generating an electrical signal using the electric charge; aclock driver having a first output terminal outputting a first clocksignal, and a second output terminal outputting a second clock signal;and a controller configured to connect the second output terminal to thesecond photo-control line during a first frame period, connect the firstoutput terminal to the second photo-control line during a second frameperiod following the first frame period, and correct a phase of a clocksignal input to the first photo-control line and the secondphoto-control line, based on data obtained in the first frame period andthe second frame period.

In some embodiments, an imaging device is provided, including: a lightsource configured to be operated by a light control signal; and a pixelarray including a plurality of pixels, wherein the plurality of pixelscomprises a plurality of general pixels, wherein the plurality ofgeneral pixels includes a first general pixel, wherein the first generalpixel includes a first pixel circuit and a second pixel circuit, whereinthe first general pixel includes a photodiode, wherein the photodiode isconfigured to generate a first electric charge in response to a receivedoptical signal output from the light source and reflected by a subject,wherein the first pixel circuit is configured to generate a firstelectrical signal based on the first electric charge, and wherein theplurality of pixels comprises a plurality of phase difference detectionpixels, wherein the plurality of phase difference detection pixelsincludes a first phase difference detection pixel, wherein the firstphase difference detection pixel is connected to an electriccharge-supplying source, wherein the electric charge-supplying source isconfigured to output a second electric charge, wherein the first phasedifference detection pixel includes a switch element, wherein the switchelement is configured to be turned on and turned off by a switch controlsignal, wherein a third pixel circuit of the first phase differencedetection pixel is configured to generate a second electrical signalbased on the second electric charge.

In some embodiments of the imaging device, the first phase differencedetection pixel comprises a second pixel node configured to receive thesecond electric charge, wherein one terminal of the switch element isconnected to the second pixel node, and the photodiode is connected to afirst pixel node.

In some embodiments of the imaging device, the plurality of generalpixels is disposed in an array form in accordance with a row directionand a column direction, and the plurality of phase difference detectionpixels is disposed in the row direction.

In some embodiments of the imaging device, the plurality of phasedifference detection pixels is disposed in a first position in thecolumn direction.

In some embodiments of the imaging device, the plurality of phasedifference detection pixels is disposed in a first position and in asecond position, and the second position is adjacent to the firstposition in the column direction.

In some embodiments of the imaging device, the plurality of phasedifference detection pixels is disposed in a first position and in asecond position separated from the first position in the columndirection.

In some embodiments of the imaging device, the plurality of generalpixels is disposed in an array form in accordance with a row directionand a column direction, the first phase difference detection pixel isdisposed separately from a second phase difference detection pixel, theplurality of phase difference detection pixels includes the second phasedifference detection pixel, and the first and second phase differencedetection pixels are surrounded by a portion of the general pixels.

In some embodiments of the imaging device, the switch control signal isthe same as the light control signal.

In some embodiments of the imaging device, the first pixel circuit andthe second pixel circuit have a same structure, the first pixel circuitcomprises a first photogate configured to be controlled by a firstphoto-control signal, and the second pixel circuit comprises a secondphotogate configured to be controlled by a second photo-control signal,the second photo-control signal has a phase difference of 180 degreesfrom the first photo-control signal, and the imaging device isconfigured to: input the first electric charge to the first pixelcircuit when the first photogate is turned on, and input the firstelectric charge to the second pixel circuit when the second photogate isturned on.

In some embodiments of the imaging device, the switch control signal isthe same as one of the first photo-control signal and the secondphoto-control signal.

In some embodiments of the imaging device, the plurality of phasedifference detection pixels is disposed in a row direction, the firstphase difference detection pixel and a second phase difference detectionpixel adjacent in the row direction are grouped into one group, and theplurality of phase difference detection pixels includes the second phasedifference detection pixel.

In some embodiments of the imaging device, the switch control signal ofthe first phase difference detection pixel and the switch control signalof the second phase difference detection pixel are the same as one ofthe first photo-control signal and the second photo-control signal ofthe first phase difference detection pixel.

In some embodiments of the imaging device, a portion of the plurality ofphase difference detection pixels is disposed in a first position in acolumn direction intersecting the row direction, and a remainder of theplurality of phase difference detection pixels is disposed in a secondposition, adjacent to the first position in the column direction, andthe portion of the plurality of phase difference detection pixelsdisposed in the first position and the remainder of the plurality ofphase difference detection pixels disposed in the second position aregrouped in different manners to each other.

Some embodiments of the imaging device include a control logicconfigured to use data obtained from the plurality of phase differencedetection pixels to correct a phase difference error between the firstphoto-control signal and the second photo-control signal.

In some embodiments of the imaging device, the control logic isconfigured to use data obtained from the plurality of general pixels togenerate a depth map including distance information between each of theplurality of general pixels and the subject.

In some embodiments of the imaging device, the light control signal andthe switch control signal are pulse width modulation (PWM) signals.

In some embodiments of the imaging device, the plurality of phasedifference detection pixels further comprises a light blocking layerblocking the received optical signal.

Also provided in some embodiments, is an image sensor including a pixelarray including a plurality of pixels, wherein a first plurality of theplurality of pixels includes a first pixel circuit having a firstphotogate connected to a pixel node, a second pixel circuit having asecond photogate connected to the pixel node, a switch element connectedto the pixel node, and an electric charge-supplying source connected tothe switch element, wherein the first photogate includes a firsttransistor and the second photogate includes a second transistor,wherein a second plurality of the plurality of pixels includes a thirdpixel circuit, wherein the third pixel circuit includes a photodiode;and a controller configured to: input a first photo-control signal tothe first photogate, input a second photo-control signal having a phasedifference of 180 degrees from the first photo-control signal to thesecond photogate, and turn on and turn off the switch element to supplyan electric charge to the pixel node.

In some embodiments of the image sensor, the controller is furtherconfigured to: generate a light control signal driving a light sourceoutputting an optical signal, and input the light control signal to theswitch element as a switch control signal to turn on and turn off theswitch element.

In some embodiments of the image sensor, the controller inputs one ofthe first photo-control signal and the second photo-control signal tothe switch element as a switch control signal to turn on and turn offthe switch element.

In some embodiments of the image sensor, the controller is furtherconfigured to adjust a phase of at least one of the first photo-controlsignal and the second photo-control signal, based on data obtained fromat least one portion of the plurality of pixels.

In some embodiments of the image sensor, the first pixel circuit isassociated with a first lens, the third pixel circuit is associated witha second lens, a first light blocking layer is configured to block lightfrom passing through the first lens, and the second lens is configuredto allow a passage of light.

In some embodiments of the image sensor, the first pixel circuit is notassociated with a photodiode.

In some embodiments of the image sensor, the electric charge-supplyingsource includes a current mirror, wherein the current mirror includestwo transistors configured with a first gate of the first transistorconnected to a second gate of the second transistor, and a referencecurrent is configured to flow through the first transistor.

In some embodiments of the image sensor, the data includes first datacorresponding to a first waveform area, second data corresponding to asecond waveform area, third data corresponding to a third waveform area,and fourth data corresponding to a fourth waveform area, wherein thecontroller is further configured to: obtain the first data from thefirst pixel circuit after a first frame time, obtain the second datafrom the second pixel circuit after the first frame time, obtain thethird data from the first pixel circuit after a second frame time,obtain the fourth data from the second pixel circuit after the secondframe time, estimate a phase error as proportional to at least one of:i) the fourth data minus the third data and ii) the second data plus apredetermined constant minus the first data, and adjust the phase of atleast one of the first photo-control signal and the second photo-controlsignal based on the estimated phase error.

Also provided in some embodiments, is an alternative image sensorincluding a pixel array including first pixels disposed along a firstphoto-control line, and second pixels disposed along a secondphoto-control line, each of the first pixels including a firstphotodiode configured to generate a first electrical charge and each ofthe second pixels including a second photodiode configured to generate asecond electric charge, and a pixel circuit configured to generate anelectrical signal using the first electric charge or the second electriccharge; a clock driver, wherein the clock driver includes a first outputterminal and a second output terminal, wherein the clock driver isconfigured to output a first clock signal at the first output terminal,and a second output signal at the second output terminal; and acontroller configured to: connect the second output terminal to thesecond photo-control line during a first frame period, connect the firstoutput terminal to the second photo-control line during a second frameperiod following the first frame period, and correct a phase of a clocksignal input to the first photo-control line and the secondphoto-control line, based on data obtained in the first frame period andthe second frame period.

In some embodiments of the alternative image sensor, the controller isfurther configured to, during the first frame period and the third frameperiod following the second frame period: connect the first outputterminal to the first photo-control line, and connect the second outputterminal to the second photo-control line.

In some embodiments of the alternative image sensor also includes acolumn selection circuit configured to connect one of the first outputterminal and the second output terminal to the second pixels, inresponse to a command from the controller.

In some embodiments of the alternative image sensor, the columnselection circuit comprises a multiplexer.

In some embodiments of the alternative image sensor, the second frameperiod repeats at predetermined periods.

In some embodiments of the alternative image sensor, the controller isfurther configured to, when the image sensor enters a wakeup mode, setthe first frame period and the second frame period.

In some embodiments of the alternative image sensor, the controller isfurther configured to set the first pixels as dummy pixels during thesecond frame period.

In some embodiments of the alternative image sensor, each of the firstphoto-control line and the second photo-control line comprises a pair ofphoto-control lines, and the clock driver is configured to input clocksignals to the pair of photo-control lines, wherein the clock signalshave a phase difference with respect to each other.

In some embodiments of the alternative image sensor the phase differenceis one of 90 degrees and 180 degrees.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a block diagram schematically illustrating an imaging deviceaccording to an embodiment of the present application.

FIGS. 2A and 2B are views schematically illustrating an image sensoraccording to an embodiment of the present application.

FIG. 3 is a block diagram schematically illustrating an imaging deviceaccording to an embodiment of the present application.

FIG. 4 is a view schematically illustrating a pixel array of an imagesensor according to an embodiment of the present application.

FIGS. 5 and 6 are circuit diagrams illustrating general pixels includedin an image sensor according to an embodiment of the presentapplication.

FIG. 7 is a view illustrating an operation of an image sensor accordingto an embodiment of the present application.

FIGS. 8A, 8B, 9A, 9B, 10A and 10B are timing diagrams illustrating anoperation of an image sensor according to an embodiment of the presentapplication.

FIG. 11 is a view schematically illustrating an image sensor accordingto an embodiment of the present application.

FIGS. 12 and 13 are circuit diagrams illustrating phase differencedetection pixels included in an image sensor according to an embodimentof the present application.

FIGS. 14A and 14B are timing diagrams illustrating an operation of phasedifference detection pixels included in an image sensor according to anembodiment of the present application.

FIGS. 15A and 15B are views schematically illustrating pixels of animage sensor according to an embodiment of the present application.

FIGS. 16 to 19 are views schematically illustrating an image sensoraccording to an embodiment of the present application.

FIGS. 20A, 20B, and 21 are views illustrating a method of grouping phasedifference detection pixels in an image sensor according to anembodiment of the present application.

FIGS. 22 and 23 are views illustrating an operation of phase differencedetection pixels included in one group in an image sensor according toan embodiment of the present application.

FIGS. 24 and 25 are views illustrating a phase difference detectionoperation using general pixels in an image sensor according to anembodiment of the present application.

FIG. 26 is a block diagram schematically illustrating an electronicdevice including an image sensor according to an embodiment of thepresent application.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the present application will bedescribed with reference to the accompanying drawings.

FIG. 1 is a block diagram schematically illustrating an imaging deviceaccording to an embodiment of the present application.

Referring first to FIG. 1, an imaging device 1 according to anembodiment of the present application may include a light source 2 and asensor unit 3. The light source 2 may include a light emitting elementthat outputs an optical signal of a specific wavelength band. Forexample, the light source 2 may include a vertical cavity surfaceemitting laser (VCSEL), a light emitting diode (LED), or the like, asthe light emitting element. The light source 2 may include a pluralityof light emitting elements arranged in an array form, and an opticalelement may be further provided on a path of an optical signal outputfrom the plurality of light emitting elements. The optical signal outputfrom the light source 2 may be an optical signal in an infraredwavelength band.

The optical signal output from the light source 2 may be reflected by asubject 4, and the optical signal reflected by the subject 4 may beinput into the sensor unit 3, as a received optical signal. The sensorunit 3 may include a pixel array having pixels that generate anelectrical signal in response to the received optical signal, acontroller that generates an image using the electrical signal generatedby the pixel array, and the like. For example, the image generated bythe controller may be a depth map including distance information of thesubject 4 and its surrounding environment.

In an embodiment of the present application, the sensor unit 3 may have,in addition to a function of generating the depth map, a proximitysensing function of sensing a presence of the subject 4 adjacent to theimaging device 1, a distance measuring function of calculating adistance between the subject 4 and the imaging device 1, and the like.The sensor unit 3 may be realized as an image sensor including a pixelarray having a plurality of pixels, a controller for controlling thepixel array, and the like. As the received optical signal output fromthe light source and reflected by the subject is accurately detected bythe sensor unit 3, the above functions may be realized more accurately.

In an example, each of the plurality of pixels may operate with aplurality of clock signals having a phase difference from each other.The phase of the clock signals input to the plurality of pixels may bedetermined based on a light control signal input to the light source 2.Operation performance of the imaging device 1 may be improved byaccurately determining a phase difference between the clock signalsinput to the plurality of pixels and the light control signal.

For example, at least one of the clock signals input to the plurality ofpixels may have the same phase as the light control signal. Actually, aphase difference may occur between the clock signal and the lightcontrol signal due to various factors, and the distance informationdetermined by the sensor unit 3 with respect to the subject 4 positionedat the same distance due to the phase difference may be different fromeach other. In an embodiment of the present application, performance ofthe imaging device 1 may be improved by detecting and compensating forunintended phase differences between clock signals input to a pluralityof pixels and light control signal input to the light source 2, orbetween clock signals.

FIGS. 2A and 2B are views schematically illustrating an image sensoraccording to an embodiment of the present application.

Image sensors 5 and 5A according to embodiments illustrated in FIGS. 2Aand 2B may be employed as the sensor unit 3 of the imaging device 1described with reference to FIG. 1. Referring first to FIG. 2A, an imagesensor 5 according to an embodiment of the present application mayinclude a first layer 6, a second layer 7 provided below the first layer6, and a third layer 8 provided below the second layer 7. The firstlayer 6, the second layer 7, and the third layer 8 may be stacked in adirection perpendicular to each other. In an embodiment, the first layer6 and the second layer 7 may be laminated to each other on a waferlevel, and the third layer 8 may be attached to a lower surface of thesecond layer 7 on a chip level. The first to third layers 6, 7, and 8may be provided as a single semiconductor package.

The first layer 6 may include a sensing area SA provided with aplurality of pixels PX, and a first pad area PA1 provided around thesensing area SA. The first pad area PA1 may include a plurality of upperpads PAD, and the plurality of upper pads PAD may be connected to padsprovided on a second pad area PA2 of the second layer 7, and to a logiccircuit LC, through a via, or the like.

Each of the plurality of pixels PX may include a photodiode forreceiving light to generate an electric charge, a pixel circuit forprocessing the electric charge generated from the photodiode, and thelike. The pixel circuit may include a plurality of transistors foroutputting a voltage corresponding to the electric charge generated fromthe photodiode.

The second layer 7 may include a plurality of elements providing thelogic circuit LC. The plurality of elements included in the logiccircuit LC may provide circuits for driving a pixel circuit provided inthe first layer 6, for example, a clock driver, a read-out circuit, anarithmetic circuit, and a timing controller. The plurality of elementsincluded in the logic circuit LC may be connected to the pixel circuitthrough the first and second pad areas PA1 and PA2. The logic circuit LCmay obtain a reset voltage and a pixel voltage from the plurality ofpixels PX to generate a pixel signal.

In an embodiment, at least one of the plurality of pixels PX may includea plurality of photodiodes disposed on the same level in a semiconductorsubstrate. Pixel signals generated from the electric charges of each ofthe plurality of photodiodes may have a phase difference from eachother, and the logic circuit LC may provide an autofocus function, basedon a phase difference of pixel signals generated from a plurality ofphotodiodes included in a single pixel PX.

The third layer 8 provided below the second layer 7 may include a memorychip MC, a dummy chip DC, and a protection layer EN sealing the memorychip MC and the dummy chip DC. The memory chip MC may be a dynamicrandom access memory (DRAM) or a static random access memory (SRAM), andthe dummy chip DC may not have a function of actually storing data. Thememory chip MC may be electrically connected to at least a portion ofthe elements included in the logic circuit LC of the second layer 7through bumps, and may store information necessary to provide anautofocus function. In an embodiment, the bumps may be micro-bumps.

Referring next to FIG. 2B, an image sensor 5A according to an embodimentof the present application may include a first layer 6A and a secondlayer 7A. The first layer 6A may include a sensing area SA provided witha plurality of pixels PX, a logic circuit LC provided with elements fordriving the plurality of pixels PX, and a first pad area PA1 providedaround the sensing area SA the logic circuit LC. The first pad area PA1may include a plurality of upper pads PAD, and the plurality of upperpads PAD may include a memory chip MC provided in the second layer 7A,through a via, or the like. The second layer 7A may include a memorychip MC, a dummy chip DC, and a protection layer EN sealing the memorychip MC and the dummy chip DC.

FIG. 3 is a block diagram schematically illustrating an imaging deviceaccording to an embodiment of the present application.

Referring to FIG. 3, an imaging device 10 may include a controller 20, apixel array 30, a light source driver 40, a light source 50, and thelike. The pixel array 30 may include a plurality of pixels PX disposedin an array form in accordance with a plurality of rows and a pluralityof columns. Each of the plurality of pixels PX may include a photodiodegenerating an electric charge in response to an optical signal incidentfrom a subject 60, a pixel circuit generating an electrical signalcorresponding to the electric charge generated by the photodiode, andthe like. For example, the pixel circuit may include a floatingdiffusion, a transfer transistor, a reset transistor, a drivingtransistor, a selection transistor, and the like. A configuration of thepixels PX may vary, depending on embodiments. As an example, each of thepixels PX may include an organic photodiode that may include an organicmaterial, unlike a silicon photodiode, or may be implemented as digitalpixels. When the pixels PX are implemented as digital pixels, each ofthe pixels PX may include a comparator, a counter converting output ofthe comparator into a digital signal and outputting the digital signal,and the like.

The controller 20 may include a plurality of circuits for controllingthe pixel array 30. For example, the controller 20 may include a clockdriver 21, a read-out circuit 22, an arithmetic circuit 23, a controllogic 24, and the like. The clock driver 21 may drive the pixel array 30in a first direction or a second direction. The first direction and thesecond direction may be directions in which the plurality of pixels PXare arranged in the pixel array 30. For example, the clock driver 21 maygenerate a transfer control signal input to a transfer gate of the pixelcircuit, a reset control signal input to a reset gate, a selectioncontrol signal input to a selection gate, a photo control signal inputto a photo gate, and the like. The first direction and the seconddirection may be defined in various ways. For example, the firstdirection may correspond to a row direction, and the second directionmay correspond to a column direction.

The read-out circuit 22 may include a correlated double sampler (CDS),an analog-to-digital converter (ADC), and the like. The correlateddouble sampler may be connected to pixels PX selected by a clock signalsupplied by the clock driver 21, through column lines, and may perform acorrelated double sampling operation to detect a reset voltage and apixel voltage. The analog-to-digital converter may convert the resetvoltage and the pixel voltage detected by the correlated double samplerinto a digital signal, and may transmit the digital signal to thearithmetic circuit 23.

The arithmetic circuit 23 may include a latch or buffer circuit, and anamplification circuit capable of temporarily storing a digital signal,and may process the digital signal received from the read-out circuit22. The clock driver 21, the read-out circuit 22, and the arithmeticcircuit 23 may be controlled by the control logic 24. The control logic24 may include a timing controller for controlling operation timings ofthe clock driver 21, the read-out circuit 22, and the arithmetic circuit23, an image signal processor for performing an image signal processingoperation. In an embodiment, the arithmetic circuit 23 may be includedin the control logic 24.

The control logic 24 may perform a signal process of data output fromthe read-out circuit 22 and the arithmetic circuit 23 to generate imagedata. For example, the image data may include a depth map. The controllogic 24 may also control a distance between the subject 60 and theimaging device 10 using the data output from the read-out circuit 22 andthe arithmetic circuit 23, or may recognize the subject 60 adjacent tothe imaging device 10, in accordance with an operation mode of theimaging device 10. Alternatively, the arithmetic circuit 23 may generatea depth map, and the control logic 24 may also perform an image processof the depth map to improve image quality.

The imaging device 10 may include the light source 50 outputting anoptical signal to the subject 60 to generate the depth map. The lightsource 50 may include at least one light emitting element, and mayinclude, for example, a semiconductor chip in which a plurality ofsemiconductor light emitting elements may be arranged in an array form.The light source 50 may be operated by the light source driver 40. Thelight source driver 40 may be controlled by the controller 20.

In an embodiment, the light source driver 40 may generate a lightcontrol signal having pulse signal characteristics to drive the lightsource 50. The light source driver 40 may generate a light controlsignal by a pulse width modulation (PWM) signal in response to a controlcommand of the controller 20, and may determine a frequency, a dutyratio, a repetition time period, and the like of the light controlsignal. For example, the controller 20 may synchronize at least one ofclock signals that the clock driver 21 inputs to the pixel array 30,with a light control signal input to the light source 50. In anembodiment, the signal synchronized with the light control signal inputto the light source 50 may be a photo-control signal that the clockdriver 21 inputs to the photogate of the pixels PX. In some embodiments,a photogate is a transistor such as a field effect transistor (FET).

The pixels PX may receive the photo-control signal from output buffersincluded in the clock driver 21. For example, pixels PX connected to asingle row line or pixels PX connected to a single column line mayreceive the same photo-control signal. Ideally, the photo-controlsignals output from the output buffers approximately simultaneously maynot have a phase difference with respect to each other, but actually, aphase difference error may occur between the photo-control signals dueto various factors. The phase difference error may also occur betweenthe light control signal and the photo-control signal.

Embodiments of the present application may detect a phase differenceerror that unintentionally appears between photo-control signals, orbetween a photo-control signal and a light control signal, andcompensate for the phase difference error. Therefore, performance of theimaging device 10 may be improved by increasing accuracy of data outputby the pixels PX.

FIG. 4 is a view schematically illustrating a pixel array of an imagesensor according to an embodiment of the present application.

Referring to FIG. 4, a pixel array 30 according to an embodiment of thepresent application may include a plurality of pixels PX, and theplurality of pixels PX may be disposed at points in which a plurality ofrow lines ROW [1] to ROW [m] and a plurality of column lines COL1 [1] toCOL1 [n], and COL2 [1] to COL2 [n] intersect. In an embodimentillustrated in FIG. 4, each of the plurality of pixels PX may beconnected to one of the plurality of row lines ROW [1] to ROW [m]. Eachof the plurality of pixels PX may be connected to one of a plurality offirst column lines COL1 [1] to COL1 [n], and a plurality of secondcolumn lines COL2 [1] to COL2 [n]. According to embodiments, the numberof row lines ROW [1] to ROW [m] and column lines COL [1] to COL [n]connected to each of the plurality of pixels PX may vary in differentranges. Extension directions of the row lines ROW [1] to ROW [m]connected to the plurality of pixels PX and the plurality of columnlines COL1 [1] to COL1 [n], and COL2 [1] to COL2 [n] may be differentfrom those illustrated in FIG. 4.

Each of the plurality of pixels PX may include a photodiode generatingan electric charge in response to an optical signal received by thepixel array 30, and include a pixel circuit outputting an electricalsignal using the electric charge generated by the photodiode. The pixelcircuit may include a photogate for allowing the electric chargegenerated by the photodiode to move, a floating diffusion foraccumulating an electric charge (in general the expression “a floatingdiffusion” may refer to “a floating diffusion portion” or “a floatingdiffusion region”), a transfer transistor connected between the floatingdiffusion and the photogate, a reset transistor for resetting thefloating diffusion, a driving transistor for amplifying a voltage of thefloating diffusion, a selection transistor for connecting the drivingtransistor to one of the column lines COL1 [1] to COL1 [n], and COL2 [1]to COL2 [n], and the like.

When the optical signal output from the light source is reflected by thesubject to be incident on the pixel array 30, the photodiodes of each ofthe plurality of pixels PX may generate electric charges in response tothe incident optical signal. The optical signal output from the lightsource, and the received optical signal reflected by the subject andincident on the pixel array 30 may have a phase difference related to adistance to the subject. In an embodiment, the imaging device may usethe phase difference to determine the distance between the imagingdevice and the subject, or to sense proximity of the subject, togenerate the depth map.

The imaging device may obtain electrical signals corresponding toelectric charges generated during different integration times, through aplurality of first column lines COL1 [1] to COL1 [n] and a plurality ofsecond column lines COL2 [1] to COL2 [n], connected to a plurality ofpixels PX during a frame. For example, electrical signals may beobtained by turning on and off the transfer transistors included in eachof the plurality of pixels PX using the transfer control signal having aphase difference of 180 degrees, through the first column lines COL1 [1]to COL1 [ n] and the second column lines COL2 [1] to COL2 [n].

FIGS. 5 and 6 are circuit diagrams illustrating general pixels includedin an image sensor according to an embodiment of the presentapplication.

Referring to FIG. 5, a pixel PX of an imaging device according to anembodiment of the present application may include a photodiode PDgenerating an electric charge in response to an optical signal, andpixel circuits PC1 and PC2 outputting an electrical signal correspondingto the electric charge generated by the photodiode PD. The pixelcircuits PC1 and PC2 may include a first pixel circuit PC1 and a secondpixel circuit PC2. The first pixel circuit PC1 may be connected to afirst sampling circuit SA1 and a first analog-to-digital converter ADC1through a first column line COL1, and the second pixel circuit PC2 maybe connected to a second sampling circuit SA2 and a secondanalog-to-digital converter ADC2 through a second column line COL2.

The first pixel circuit PC1 may include a first phototransistor PX1connected to the photodiode PD, a first transfer transistor TX1, a firstfloating diffusion FD1 accumulating an electric charge generated fromthe photodiode PD, and a plurality of first circuit elements RX1, DX1,and SX1. As used herein, a phototransistor includes a transistor. Theplurality of first circuit elements RX1, DX1, and SX1 may include afirst reset transistor RX1, a first driving transistor DX1, a firstselection transistor SX1, and the like. The second pixel circuit PC2 mayhave a structure similar to that of the first pixel circuit PC1. Controlsignals TG1, RG1, and SEL1 for controlling the first transfer transistorTX1, the first reset transistor RX1, and the first selection transistorSX1 may be input by a row driver of the imaging device.

When the first reset transistor RX1 is turned on, a voltage of the firstfloating diffusion FD1 may be reset to a power supply voltage VDD, andthe selection transistor SX1 may be turned on such that the firstsampling circuit SAl may detect a first reset voltage. During a firstexposure time until the first reset transistor RX1 is turned off and thefirst transfer transistor TX1 is turned on, the photodiode PD may beexposed to light to generate an electric charge.

When the first transfer transistor TX1 is turned on, an electric chargegenerated in the photodiode PD and accumulated in the firstphototransistor PX1 may be transferred to the first floating diffusionFD1. The first sampling circuit SA1 may detect a first pixel voltage inresponse to the turn on of the first selection transistor SX1. The firstanalog-to-digital converter may convert a difference between the firstreset voltage and the first pixel voltage into first raw data DATA1 in adigital form.

An operation of the second pixel circuit PC2 may be similar to that ofthe first pixel circuit PC1. A second phototransistor PX2 may not beturned on at the same time as the first phototransistor PX1. Therefore,a second pixel voltage output from the second pixel circuit PC2 throughthe second column line COL2 may correspond to an electric chargegenerated by exposing the photodiode PD to light during a secondexposure time different from the first exposure time. The secondanalog-to-digital converter ADC2 may convert a difference between asecond reset voltage and the second pixel voltage into second raw dataDATA2.

In an embodiment of the present application, an imaging device mayoperate in a global shutter mode. For example, after the first andsecond reset transistors RX1 and RX2 included in each of the pixels PXincluded in the imaging device are all turned on to reset the pixels PXsimultaneously, the photodiode PD included in the pixels PX may beexposed to light during a predetermined exposure time to generate anelectric charge. An amount of exposure time during which the photodiodePD is exposed to light may vary, depending on an operation mode of theimaging device. During the exposure time, clock signals having acomplementary relation to each other may be input to the firstphototransistor PX1 and the second phototransistor PX2, and the electriccharge generated from the photodiode PD may be stored in at least one ofthe first phototransistor PX1 and the second phototransistor PX2. Theclock signals input to the first phototransistor PX1 and the secondphototransistor PX2 may be controlled by synchronizing with the lightcontrol signal input to the light source of the imaging device.

For example, during a first time, a first photo-control signal PG1 inputto the first phototransistor PX1 may have the same phase as a lightcontrol signal, and a second photo-control signal PG2 input to thesecond phototransistor PX2 may have a phase difference of 180 degreesfrom a light control signal. Also, during a second time after the firsttime, the first photo-control signal PG1 may have a phase difference of90 degrees from the light control signal, and the second transfercontrol signal TG2 may have a phase difference of 270 degrees from thelight control signal. The image sensor may use the first raw data DATA1and the second raw data DATA2 acquired during the first time, and thefirst raw data DATA1 and the second raw data DATA2 acquired during thesecond time, to recognize a subject or determine a distance to thesubject. In an example, each of the first time and the second time maybe a frame period of the image sensor.

Pixels PX adjacent to each other in a column direction in which thecolumn lines COL1 and COL2 extend may share the first photo-controlsignal PG1 and the second photo-control signal PG2. In an embodiment,the first phototransistor PX1 included in each of the pixels PX adjacentto each other in the column direction may be connected to the firstphoto-control line, and may receive the same first photo-control signalPG1. Similarly, the second phototransistor PX2 included in each of thepixels PX adjacent to each other in the column direction may beconnected to the second photo-control line, and may receive the samesecond photo-control signal PG2. For example, the first photo-controlline and the second photo-control line may be lines extending in thecolumn direction.

Referring to FIG. 6, in a pixel PX of an image sensor according to anembodiment of the present application, a plurality of pixel circuitsPC1, PC2, PC3, and PC4 may be connected to a single photodiode PD. In anembodiment illustrated in FIG. 6, first to fourth pixel circuits PC1,PC2, PC3, and PC4 are illustrated to be connected to the photodiode PD.According to embodiments, the number thereof may vary in differentranges. The first to fourth pixel circuits PC1, PC2, PC3, and PC4 mayhave substantially the same structure as each other.

Operations of the first to fourth pixel circuits PC1, PC2, PC3, and PC4may be similar to that described above with reference to FIG. 5. Firstto fourth phototransistors PX1, PX2, PX3, and PX4 included in the firstto fourth pixel circuits PC1, PC2, PC3, and PC4 may operate in differentphases, while the photodiode PD is exposed to light. For example, thefirst photo-control signal PG1 input to the first photo-transistor PX1and the second photo-control signal PG2 input to the secondphoto-transistor PX2 may have a phase difference of 180 degrees fromeach other. A third photo-control signal PG3 and a fourth photo-controlsignal PG4 may have a phase difference of 180 degrees from each other,and the third photo-control signal PG3 may have a phase difference of 90degrees from the first photo-control signal PG1. In an embodiment, thefirst to fourth photo-control signals PG1, PG2, PG3, and PG4 may havethe same period as the light control signal, and may have a duty ratiosmaller than the light control signal. For example, the duty ratios ofthe first to fourth photo-control signals PG1, PG2, PG3, and PG4 may be½ of the duty ratio of the light control signal.

The image sensor may generate a depth map using pixel voltages obtainedfrom electric charges stored in the first to fourth phototransistorsPX1, PX2, PX3, and PX4 by the phase difference operation as describedabove. In the read-out operation, first data corresponding to theelectric charge stored in the first phototransistor PX1 may be outputthrough the first column line COL1, and second data corresponding to theelectric charge stored in the second phototransistor PX2 may be outputthrough the second column line COL2. Further, third data correspondingto the electric charge stored in the third phototransistor PX3 may beoutput through the third column line COL3, and fourth data correspondingto the electric charge stored in the fourth phototransistor PX4 may beoutput through the fourth column line COL4.

According to embodiments, the first pixel circuit PC1 and the thirdpixel circuit PC3 may be connected to a single column line, the secondpixel circuit PC2 and the fourth pixel circuit PC4 may be connected to asingle column line. In a similar manner to the above, the pixels PXdisposed in the same position in the row direction and disposed adjacentto each other in the column direction may share the first to fourthphoto-control signals PG1, PG2, PG3, and PG4.

FIG. 7 is a view illustrating an operation of an image sensor accordingto an embodiment of the present application.

FIG. 7 is a view provided to explain an operation of global shutter ofan image sensor. Referring to FIG. 7, photodiodes of a plurality ofpixels included in a pixel array during a reset time T_(RST) may bereset simultaneously. In an example, a clock driver may reset thephotodiodes by turning on a reset transistor included in a pixel circuitto connect the photodiode to a predetermined power supply voltage.

When the photodiodes are reset, the photodiodes included in theplurality of pixels may be exposed to light during an exposure timeT_(EX) to generate an electric charge. As used herein “reset” may referto establishing points within a circuit at a predetermined voltage. Forexample, the exposure time T_(EX) may be determined by an operatingenvironment of the image sensor, shutter speed, diaphragm value, and thelike.

When the exposure time T_(EX) elapses, the clock driver may scan aplurality of row lines connected to the plurality of pixels. A read-outcircuit may perform a read-out operation for the plurality of pixels insequence that the clock driver scans the plurality of row lines. Theread-out circuit may read a reset voltage and a pixel voltage from eachof the plurality of pixels during a read-out time T_(RO).

In order for the read-out circuit to read the reset voltage and thepixel voltage during the read-out time T_(RO), the electric chargegenerated by the photodiodes during the exposure time T_(EX) may bestored in a storage area of the pixel circuit. In an example, thestorage area may be a phototransistor of the pixel circuit. An electriccharge stored in the storage area may move to a floating diffusion ofthe pixel circuit in response to the turn on of a transfer transistor.The read-out circuit may read the reset voltage of the plurality ofpixels, before the transfer transistor is turned on, i.e., while theelectric charge is stored in the storage area. The read-out circuit mayread the pixel voltage of the plurality of pixels, after the transfertransistor is turned on by the clock driver to move the electric chargein the storage area to the floating diffusion.

FIGS. 8A, 8B, 9A, 9B, 10A and 10B are timing diagrams illustrating anoperation of an image sensor according to an embodiment of the presentapplication.

FIGS. 8A and 8B illustrate an output optical signal, a received opticalsignal, a first photo-control signal PG1, and a second photo-controlsignal PG2 during a first frame period and a second frame period. Inembodiments illustrated in FIGS. 8A and 8B, an output optical signal maybe an optical signal output from a light source that operates in a PWMmanner, and may have the same period and duty ratio as a light controlsignal input to the light source. FIGS. 8A and 8B may be viewsillustrating the first photo-control signal PG1 and the secondphoto-control signal PG2, input to the pixels during an exposure timeexposing a photodiode PD to light, after resetting the pixelssimultaneously, in an imaging device operating in a global shutter mode.

Referring to FIG. 8A, an output optical signal, and a received opticalsignal generated by reflecting the output optical signal by a subjectmay have a phase difference (Ø). During a first frame period, a firstphoto-control signal PG1 may have a phase difference of 0 degree fromthe output optical signal, and a second photo-control signal PG2 mayhave a phase difference of 180 degrees from the output optical signal.Therefore, an electric charge generated from a photodiode PD during afirst exposure time (ex1) may be accumulated in a first phototransistorcontrolled by the first photo-control signal PG1, and an electric chargegenerated from a photodiode PD during a second exposure time (ex2) maybe accumulated in a second phototransistor controlled by the secondphoto-control signal PG2.

Next, referring to FIG. 8A, during a second frame period, a firstphoto-control signal PG1 may have a phase difference of 90 degrees fromthe output optical signal, a second photo-control signal PG2 may have aphase difference of 270 degrees from the output optical signal.Therefore, a first exposure time (ex1) and a second exposure time (ex2)in which a photodiode PD is exposed to light during the second frameperiod may be different from the first exposure time (ex1) and thesecond exposure time (ex2) during the first frame period, respectively.During the second frame period, the first exposure time (ex1) may belonger than the second exposure time (ex2).

When the exposure time ends, a controller of an imaging device may reada pixel voltage and a reset voltage from pixels included in a pixelarray. For example, the controller of the imaging device may read thepixel voltage and the reset voltage in each of a first column line and asecond column line connected to the pixel in accordance with a rollingmethod, and may calculate a difference therebetween. The differencebetween the pixel voltage and the reset voltage may be used as raw data.

The controller of the imaging device may determine a distance betweenthe subject and the pixel by using the raw data obtained through thefirst column line and the second column line connected to the pixel ineach of the first frame period and the second frame period. Thecontroller of the imaging device may also generate a depth map using thedistance between each of the pixels and the subject. For example, if rawdata output through each of the first column line and the second columnline during the first frame period are defined as A0 and A2, and rawdata output through each of the first column line and the second columnline during the second frame period are defined as A1 and A3, a distance(d) between the pixel and the subject may be determined as follows. Inthe following Equation 1, c refers to a speed of light, and fm refers toa frequency of a light control signal input to a light source.

$\begin{matrix}{{\varphi = {\arctan\left( \frac{{A1} - {A3}}{{A0} - {A2}} \right)}}{d = {\frac{c}{2f_{m}}\frac{\varphi}{2\pi}}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Equation 1 is given as an example, other functions of the waveforms ofFIGS. 8A and 8B may be used to estimate the depth d.

FIGS. 9A and 9B illustrate an output optical signal, a received opticalsignal, a first photo-control signal PG1, and a second photo-controlsignal PG2 during a first frame period and a second frame period. In anembodiment illustrated in FIGS. 9A and 9B, unlike the embodimentillustrated in FIGS. 8A and 8B, a phase difference error (θ) may occurbetween the output optical signal, and the first photo-control signalPG1 and the second photo-control signal PG2. For example, referring toFIG. 9A, due to the phase difference error (θ), a phase differencebetween the first photo-control signal PG1 and the output optical signalmay be greater than 0 degree, and a phase difference between the secondphoto-control signal PG2 and the output optical signal may be greaterthan 180 degrees. Therefore, a first exposure time (ex1) and a secondexposure time (ex2) appearing in the first frame period and the secondframe period may also be different from those of a case in which thereis no phase difference error (θ).

Since the first exposure time (ex1) and the second exposure time (ex2)appearing in the first frame period and the second frame period may bedifferent due to the phase difference error (θ), a distance between thepixel and the subject may not be accurately measured. In an embodimentof the present application, by arranging phase difference detectionpixels for detecting the phase difference error (θ) in the pixel array,the phase difference error (θ) may be detected, and compensation datafor compensating the phase difference error (θ) may be generated.Alternatively, the phase difference error (θ) may be detected byshifting the first photo-control signal PG1 and the second photo-controlsignal PG2 input to the pixels in each of the two frame periods, withoutthe phase difference detection pixels.

Next, FIGS. 10A and 10B may be timing diagrams with or without a phasedifference error (θ) in an image sensor in which one pixel includes fourpixel circuits. FIG. 10A may be a timing diagram corresponding to a casein which a phase difference error (θ) does not exist, and FIG. 10B maybe a timing diagram corresponding to a case in which a phase differenceerror (θ) exists.

Referring to FIGS. 10A and 10B, one pixel in an image sensor may includefour pixel circuits. First to fourth phototransistors included in thefour pixel circuits may receive first to fourth photo-control signalsPG1 to PG4. Each of the first to fourth photo-control signals PG1 to PG4may have a predetermined phase difference from an output optical signal,and may have a duty ratio lower than that of the output optical signal.The first photo-control signal PG1 may have a phase difference of 0degree from the output optical signal, and each of the second to fourthphoto-control signals PG2 to PG4 may have phase differences of 90degrees, 180 degrees, and 270 degrees. For example, duty ratios of thefirst to fourth photo-control signals PG1 to PG4 may be ½ of duty ratiosof output optical signals.

Referring to FIG. 10A, a turn on time of a first photo-control signalPG1 may not overlap a time at which a received optical signal enters aphotodiode. The turn on time of each of the second to fourthphoto-control signals PG2 to PG4 may overlap a time at which a receivedoptical signal enters a photodiode, in amounts of the second to fourthexposure times (ex2 to ex4), respectively. The image sensor may measurea distance from the pixel to a subject by the method described abovewith reference to the above Equation 1. Therefore, the distance betweenthe pixel and the subject may be measured with data acquired during asingle frame period.

In an embodiment illustrated FIG. 10B, a phase difference error (θ) mayexist. Therefore, whether or not a turn on time of first to fourthphoto-control signals PG1 to PG4 and a received optical signal overlapeach other may be different from the embodiment illustrated in FIG. 10A.For example, in an embodiment illustrated in FIG. 10B, due to the phasedifference error (θ), only turn on times of a second photo-controlsignal PG2 and a third photo-control signal PG3 may overlap a time atwhich a received optical signal enters a photodiode. Due to the phasedifference error (θ), a distance between a pixel detected by an imagesensor and a subject may be different, and an error may occur in a depthmap. As described above, in an embodiments of the present application,the phase difference error (θ) may be detected by using phase differencedetection pixels for detecting the phase difference error (θ), or byshifting the photo-control signals PG1 to PG4 in each of the two frameperiods, and inputting the same into the pixels.

FIG. 11 is a view schematically illustrating an image sensor accordingto an embodiment of the present application. FIGS. 12 and 13 are circuitdiagrams illustrating phase difference detection pixels included in animage sensor according to an embodiment of the present application.

Referring to FIG. 11, an image sensor 100 according to an embodiment ofthe present application may include a pixel array 110, a clock driver120, a read-out circuit 130, an arithmetic circuit 140, and the like.The pixel array 110 may include a plurality of pixels 111 and 112arranged in a row direction and a column direction. In an example, thepixel array 110 may include a plurality of general pixels 111 and aplurality of phase difference detection pixels 112. The general pixels111 may be arranged in an array form in the row direction and the columndirection, and the phase difference detection pixels 112 may be arrangedin the row direction. The number and arrangement of the phase differencedetection pixels 112 may be variously changed according to embodiments.

For example, the clock driver 120 may be connected to the plurality ofpixels through a plurality of photo-control lines. The plurality ofphoto-control lines may be lines for inputting photo-control signals toeach of the pixels. The read-out circuit 130 may be connected to thepixels through a plurality of column lines connected to selectiontransistors of the pixels.

In an embodiment, the phase difference detection pixels 112 may have astructure, different from the general pixels 111. Hereinafter, the phasedifference detection pixels 112 will be described with reference toFIGS. 12 and 13.

Referring first to FIG. 12, a phase difference detection pixel DPXincluded in an image sensor according to an embodiment of the presentapplication may include a first pixel circuit PC1, a second pixelcircuit PC2, an electric charge circuit CC, and the like. The firstpixel circuit PC1, the second pixel circuit PC2, and the electric chargecircuit CC may be connected to a pixel node PN. The first pixel circuitPC1 and the second pixel circuit PC2 may be similar to those describedabove with reference to FIG. 5. For example, a pixel circuit included inthe phase difference detection pixel DPX may have the same structure asa pixel circuit included in a general pixel. For example, a firstphototransistor PX1 may receive a first photo-control signal PG1 througha first photo-control line connected to a clock driver, a secondphototransistor PX2 may receive a second photo-control signal PG2through a second photo-control line connected to a clock driver.

In some embodiments, the electric charge-supplying source, CC, includesa current mirror. An example of a current mirror includes twotransistors configured with a first gate of the first transistorconnected to a second gate of the second transistor, and a referencecurrent is configured to flow through the first transistor.

In the phase difference detection pixel DPX, the electric charge circuitCC may be connected to the pixel node PN, instead of a photodiode. Theelectric charge circuit CC may output an electric charge to the pixelnode PN. In an example, the electric charge circuit CC may include anelectric charge-supplying source CS for outputting an electric charge,and a switch element SW connected between the electric charge-supplyingsource CS and the pixel node PN. The switch element SW may be turnedon/off by a switch control signal SG.

Referring to FIG. 13, a phase difference detection pixel DPX included inan image sensor according to an embodiment of the present applicationmay include first to fourth pixel circuits PC1 to PC4, an electriccharge circuit CC, and the like. The first to fourth pixel circuits PC1to PC4 and the electric charge circuit CC may be connected to a pixelnode PN. The first to fourth pixel circuits PC1 to PC4 may be similar tothose described above with reference to FIG. 6. The pixel circuits ofthe phase difference detection pixel DPX may have the same structure aspixel circuits of a general pixel including a photodiode.

The electric charge circuit CC may supply an electric charge to thepixel node PN as described above with reference to FIG. 12. The electriccharge circuit CC may include a switch element SW and an electriccharge-supplying source CS, connected in series, and the switch elementSW may be turned on and off by a switch control signal SG to supply anelectric charge output from the electric charge-supplying source CS tothe pixel node PN.

In embodiments illustrated in FIGS. 12 and 13, a switch control signalSG input to a switch element SW may be the same signal as a lightcontrol signal input to a light source of an imaging device.Hereinafter, an operation of a phase difference detection pixel DPX willbe described in more detail with reference to FIGS. 14A and 14B.

FIGS. 14A and 14B are timing diagrams illustrating an operation of phasedifference detection pixels included in an image sensor according to anembodiment of the present application.

In embodiments illustrated in FIGS. 14A and 14B, an output opticalsignal may be an optical signal output from a light source that operatesin a PWM manner, and may have the same period and duty ratio as a lightcontrol signal input to the light source. A switch control signal SG maybe the same signal as the light control signal. Therefore, the outputoptical signal and the switch control signal SG may have the same periodand duty ratio, and a phase difference between the output optical signaland the switch control signal SG may be 0 degree.

An embodiment described with respect to FIG. 14A may be an ideal case inwhich an unintended phase difference error between a light controlsignal input to a light source of an imaging device, and a firstphoto-control signal PG1 and a second photo-control signal PG2 may notoccur. Referring to FIG. 14A, during a first frame period, the firstphoto-control signal PG1 may be a signal having a phase difference of 0degree from the light control signal, and the second photo-controlsignal PG2 may be a signal having a phase difference of 180 degrees fromthe light control signal. Therefore, in an ideal case, an electriccharge output from an electric charge-supplying source CS during thefirst frame period may all be stored in a first phototransistor PX1.

During a second frame period following the first frame period, the firstphoto-control signal PG1 may have a phase difference of 90 degrees fromthe light control signal, and the second photo-control signal PG2 mayhave a phase difference of 270 degrees from the light control signal.Therefore, in an ideal case, during the second frame period, theelectric charges output from the electric charge-supplying source CS maybe divided by ½ and be stored in the first phototransistor PX1 and asecond phototransistor PX2.

An embodiment described with reference to FIG. 14B may be an example inwhich an unintended phase difference error (θ) between a light controlsignal input to a light source of an imaging device, and a firstphoto-control signal PG1 and a second photo-control signal PG2 mayoccur. Referring to FIG. 14B, during a first frame period, a phasedifference error (θ) may occur between the first photo-control signalPG1 and the light control signal. Due to the phase difference error (θ),a phase difference between the second photo-control signal PG2 and thelight control signal may be 180 degrees+θ. Therefore, electric chargesoutput from an electric charge-supplying source CS during the firstframe period may be divided and stored in a first phototransistor PX1and a second phototransistor PX2.

In a second frame period following the first frame period, the firstphoto-control signal PG1 may have a phase difference of 90 degrees+θfrom the light control signal, and the second photo-control signal PG2may have a phase difference of 270 degree+θ from the light controlsignal. Therefore, in the embodiment illustrated in FIG. 14B, theelectric charge output from the electric charge-supplying source CSduring the second frame period may be stored more in the secondphototransistor PX2 than in the first phototransistor PX1.

As a result, when a case in which the phase difference error (θ) occursis compared with a case in which the phase difference error (θ) does notoccur, a difference may occur between data output from a phasedifference detection pixel DPX. An imaging device and an image sensoraccording to an embodiment of the present application may detect whetheror not the phase difference error (θ), a magnitude thereof, and thelike, by inputting a light control signal as a switch control signal SGto a switch element SW of a phase difference detection pixel DPX, andusing data acquired from the phase difference detection pixel DPX. Whenthe phase difference error (θ) is detected, a clock driver may reflect acompensation value, capable of offsetting the phase difference error(θ), to a first photo-control signal PG1 and a second photo-controlsignal PG2, input to a general pixel PX. Therefore, the phase differenceerror (θ) may be eliminated; and performance of the imaging device andthe image sensor may be improved.

For example, in FIG. 14B, data used for phase difference errorcorrection includes first data corresponding to a first waveform areasuch as the hashed area of the waveform PG1 during the first frame,second data corresponding to a second waveform area such as the hashedarea of the waveform PG2 during the first frame, third datacorresponding to a third waveform area such as the hashed area of thewaveform PG1 during the second frame, and fourth data corresponding to afourth waveform area such as the hashed area of the waveform PG2 duringthe second frame. In some embodiments, a controller obtains the firstdata from the first pixel circuit such as PC3 after a first frame time,obtains the second data from the second pixel circuit such as PC4 afterthe first frame time, obtains the third data from the first pixelcircuit PC3 after a second frame time, and obtains the fourth data fromthe second pixel circuit PC4 after the second frame time. The controllerthen estimates a phase error θ (see FIG. 14B) as proportional to atleast one of: i) the fourth data minus the third data and ii) the seconddata plus a predetermined constant minus the first data. The controllerthen adjusts the phase of at least one of the first photo-control signalPG1 (in PC1 of FIG. 6) and the second photo-control signal PG2 (in PC2of FIG. 6) based on the estimated phase error; the estimated θ. Thusinformation from DPX of FIG. 12 is used to improve the clocking ofcircuits in PX of FIG. 6. This leads to less error in estimating depth,d, using an arrangement such as pixel array 30 in FIG. 3.

FIGS. 15A and 15B are views schematically illustrating pixels of animage sensor according to an embodiment of the present application. Forexample, FIGS. 15A and 15B may be views illustrating a portion of thepixel array 110 of the image sensor 100 illustrated in FIG. 11.

In an embodiment illustrated in FIG. 15A, a pixel array 110 may includea general pixel 111 and a phase difference detection pixel 112. Thegeneral pixel 111 and the phase difference detection pixel 112 may beformed in a semiconductor substrate 113, and may be separated from eachother by a pixel separation layer DTI. The general pixel 111 and thephase difference detection pixel 112 may commonly include a circuitinsulation layer 116, an optical insulation layer 117, a micro-lens 119,and the like.

An embodiment illustrated in FIG. 15A is illustrated that only thegeneral pixel 111, not the phase difference detection pixel 112,includes a photodiode PD. Alternatively, the phase difference detectionpixel 112 may include a photodiode PD. The phase difference detectionpixel 112 may include a light blocking layer 118 formed of an opaquematerial that does not transmit light, and the light blocking layer 118may block an optical signal incident on the phase difference detectionpixel 112.

Next, referring to FIG. 15B, a micro-lens 119 and an optical insulationlayer 117 may not be formed in a phase difference detection pixel 112Aof a pixel array 110A. In a manufacturing process of the pixel array110A, after a photodiode PD and a pixel separation layer DTI may beformed in the semiconductor substrate 113, and pixel circuits 114 and115 may be formed, a light blocking layer 118A may be formed only in anarea corresponding to the phase difference detection pixel 112A. Theoptical insulation layer 117 and the micro-lenses 119 may be formed inan area corresponding to a general pixel 111. According to embodiments,a photodiode PD may be formed in the phase difference detection pixel112A.

FIGS. 16 to 19 are views schematically illustrating an image sensoraccording to an embodiment of the present application.

Referring first to FIG. 16, an image sensor 200 according to anembodiment of the present application may include a pixel array 210, aclock driver 220, a read-out circuit 230, a arithmetic circuit 240, andthe like. The pixel array 210 may include a plurality of pixels 211 and212 arranged in a row direction and a column direction. In an example,the pixel array 210 may include a plurality of general pixels 211 and aplurality of phase difference detection pixels 212. The general pixels211 may be arranged in an array form in the row direction and the columndirection, and the phase difference detection pixels 212 may be arrangedin the row direction. In an embodiment illustrated in FIG. 16, the phasedifference detection pixels 212 may be disposed along a lowermost rowline in the pixel array 210.

Operations of the clock driver 220, the read-out circuit 230, and thearithmetic circuit 240 may be similar to those described above withreference to FIG. 11. In an example, the clock driver 220 may inputphoto-control signals to each of the pixels 211 and 212 throughphoto-control lines in the column direction. For example, the pixels 211and 212 arranged in the column direction, in the same position in therow direction, may be connected to the same photo-control line, and mayreceive the same photo-control signal during an exposure time of aglobal shutter operation.

Referring to FIG. 17, in a pixel array 310 of an image sensor 300, phasedifference detection pixels 312 and 313 may be arranged along anuppermost row line and a lowermost row line. General pixels 311 may bedisposed between the phase difference detection pixels 312 and 313 in acolumn direction. Operations of a clock driver 320, a read-out circuit330, and an arithmetic circuit 340 may be similar to those describedabove.

Referring to FIG. 18, in a pixel array 410 of an image sensor 400, phasedifference detection pixels 412 may be surrounded by general pixels 411,and may be disposed separately from each other. Operations of a clockdriver 420, a read-out circuit 430, and an arithmetic circuit 440 may besimilar to those described above.

In an embodiment illustrated in FIG. 18, a portion of photo-controllines may not be connected to the phase difference detection pixels 412.An interpolation method may be used to compensate for a phase differenceerror of the photo-control signal input to the photo-control lines, notconnected to the phase difference detection pixels 412. In an embodimentillustrated in FIG. 18, from the phase difference detection pixels 412,phase difference errors of the photo-control signals input toeven-numbered photo-control lines may be obtained, and the obtainedphase difference errors may be used to estimate phase difference errorsof the photo-control signals input to odd-numbered photo-control linesby an interpolation method.

Next, referring to FIG. 19, in a pixel array 510 of an image sensor 500,phase difference detection pixels 512 and 513 may be arranged along tworow lines located at an uppermost terminal. General pixels 511 may bedisposed at a lower terminal of the phase difference detection pixels512 and 513 in a column direction. Operations of a clock driver 520, aread-out circuit 530, and an arithmetic circuit 540 may be similar tothose described above.

In an embodiment illustrated in FIG. 19, a switch control signal inputto the phase difference detection pixels 512 and 513 may be a lightcontrol signal input to a light source constituting the image sensor 500and an imaging device. According to embodiments, the switch controlsignal may be other than a light control signal. In an example, a switchcontrol signal input to each of the phase difference detection pixels512 and 513 may be one of photo-control signals input to the phasedifference detection pixels 512 and 513.

In order to use one of the photo-control signals input to the phasedifference detection pixels 512 and 513 as a switch control signal, apair of phase difference detection pixels adjacent to each other in arow direction may be grouped into a single group. Hereinafter, a moredetailed description will be given with reference to FIGS. 20 to 23.

FIGS. 20 and 21 are views illustrating a method of grouping phasedifference detection pixels in an image sensor according to anembodiment of the present application. FIGS. 22 and 23 are viewsillustrating an operation of phase difference detection pixels includedin one group in an image sensor according to an embodiment of thepresent application.

FIGS. 20A and 20B are views for explaining a grouping method in anembodiment in which phase difference detection pixels are successivelyarranged along at least one row line in an image sensor. FIG. 20A may bea view corresponding to a grouping method during a first frame period,and FIG. 20B may be a view corresponding to a grouping method during asecond frame period.

Referring first to FIG. 20A, remaining phase difference detectionpixels, except for a first phase difference detection pixel DPX0 and thelast phase difference detection pixel DPXN-1, may be grouped. A pair ofphase difference detection pixels adjacent in the row direction may begrouped into a single group. When the number of phase differencedetection pixels is N, the number of groups during the first frameperiod may be (N/2−1).

Next, referring to FIG. 20B, all phase difference detection pixels maybe grouped during the second frame period. Therefore, when the number ofphase difference detection pixels is N, the number of groups during thesecond frame period may be N/2. Image sensors according to embodimentsillustrated in FIGS. 20A and 20B may detect phase difference errors fortwo frame periods, and may generate compensation data for compensatingthe phase difference errors.

FIG. 21 may be a view illustrating a grouping method in an embodiment inwhich phase difference detection pixels are successively arranged alongtwo or more row lines in an image sensor. Referring to FIG. 21, phasedifference detection pixels included in a first row line ROW [0], andphase difference detection pixels included in a second row line ROW [1]may be grouped in a different manner to each other. Therefore, unlikeembodiments illustrated in FIG. 20, an image sensor according to anembodiment illustrated in FIG. 21 may detect a phase difference erroronly by one frame period, and may generate compensation data forcompensating the phase difference error.

FIG. 22 may be a circuit diagram illustrating a first phase differencedetection pixel DPX1 and a second phase difference detection pixel DPX2included in a single group. FIG. 23 may be a timing diagram forexplaining operations of a first phase difference detection pixel DPX1and a second phase difference detection pixel DPX2. In embodimentsillustrated in FIGS. 22 and 23, a first photo-control signal PGA1 and asecond photo-control signal PGA2 in each of the first phase differencedetection pixel DPX1 and the second phase difference detection pixelDPX2 may have a phase difference of 180 degrees from each other.

A switch element SW1 of the first phase difference detection pixel DPX1and a switch element SW2 of the second phase difference detection pixelDPX2 may receive the first photo-control signal PGA1 of the first phasedifference detection pixel DPX1 as switch control signals SG1 and SG2.As illustrated in FIG. 23, when a phase difference error (θ) is presentbetween photo-control signals PGA1 and PGB1 input to the first phasedifference detection pixel DPX1 and photo-control signals PGA2 and PGB2input to the second phase difference detection pixel DPX2, data obtainedin each of the first phase difference detection pixel DPX1 and thesecond phase difference detection pixel DPX2 may be different from eachother.

Therefore, a phase difference error (θ) may be detected by inputting oneof the photo-control signals PGA1 and PGB1 input to the first phasedifference detection pixel DPX1 to the first phase difference detectionpixel DPX1 and the second phase difference detection pixel DPX2 as theswitch control signals SG1 and SG2. The phase difference error (θ) maybe an error between a photo-control line connected to the first phasedifference detection pixel DPX1 and a photo-control line connected tothe second phase difference detection pixel DPX2.

Referring again to FIG. 20, when the phase difference detection pixelsare arranged along one row line ROW [0] in the image sensor, two frameperiods may be required to detect phase difference errors between columnlines adjacent to each other. In each of the two frame periods, thephase difference detection pixels may be grouped in different ways. Whenthe phase difference detection pixels are arranged along the two rowlines ROW [0] and ROW [1], as illustrated in FIG. 21, a phase differenceerror between photo-control lines adjacent to each other in only oneframe period may be detected by grouping phase difference detectionpixels differently in each of the two row lines ROW [0] and ROW [1].When detecting the phase difference error between the adjacentphoto-control lines, one of the photo-control lines may be selected as areference line, and compensation data needed for compensating the phasedifference error may be calculated by calculating accumulated value ofthe phase difference error with respect to each photo-control line,based on the reference line. For example, the compensation data may becalculated by an operation circuit or a control logic of the imagesensor. Based on the compensation data, the control logic may determinethe photo-control signal that the clock driver inputs to eachphoto-control line.

FIGS. 24 and 25 are views illustrating a phase difference detectionoperation using general pixels in an image sensor according to anembodiment of the present application.

In an embodiment described with respect to FIGS. 24 and 25, an imagesensor 600 may include a pixel array 610, a clock driver 620, a columnselection circuit 625, a read-out circuit 630, an arithmetic circuit640, and the like. The pixel array 610 of the image sensor 600 may notinclude phase difference detection pixels, and the like. For example,the pixel array 610 may include only general pixels. FIGS. 24 and 25 maybe views for explaining operation of the image sensor 600 in successivefirst frame period and second frame period, respectively.

The pixel array 610 may include a plurality of photo-control linesconnected to pixels, and the plurality of photo-control lines may beconnected to an output terminal of the clock driver 620, to receiveclock signals. The clock signals may be photo-control signals forstoring an electric charge generated from a photodiode in aphototransistor by turning the phototransistor on and off during aexposure time of the pixels. Therefore, a pair of photo-control linesmay be connected to one pixel, and clock signals input to the pair ofphoto-control lines may have a phase difference of 90 degrees or 180degrees.

There may be a phase difference between the photo-control signals inputto different column lines. Referring first to FIG. 24, each of thephoto-control lines during the first frame period may be connected tothe output terminal of the clock driver 620 corresponding to thephoto-control lines. In an example, a first photo-control line may beconnected to a first output terminal of the clock driver 620, and asecond photo-control line may be connected to a second output terminalof the clock driver 620.

The clock signals output from each of the output terminals of the clockdriver 620 may have a predetermined phase difference. For example, aphase difference dl may exist between the first photo-control line andthe second photo-control line. The phase difference dl may be a phasedifference between a first clock signal output from the first outputterminal of the clock driver 620 and a second clock signal output fromthe second output terminal of the clock driver 620. Similarly, a phasedifference d2 may exist between the second clock signal and a thirdclock signal, and the phase difference between the first clock signaland the third clock signal may be determined as d1+d2.

Referring now to FIG. 25, output terminals of a clock driver 620 may beshifted one by one, and may be input to photo-control lines, by a columnselection circuit 625 during a second frame period. An n^(th)photo-control line connected to an n^(th) output terminal of the clockdriver 620 in a first frame period may be connected to an (n-1)^(th)output terminal of the clock driver 620 during a second frame period.During the second frame period, a first photo-control line may be notconnected to an output terminal of the clock driver 620. Therefore,pixels connected to the first photo-control line may be set as dummypixels.

A second photo-control line may be connected to a second output terminalof the clock driver 620 during the first frame period, and may beconnected to a first output terminal of the clock driver 620 during thesecond frame period. A phase difference between a first clock signal anda second clock signal output from the first output terminal and thesecond output terminal of the clock driver 620 may be d1. Similarly,during the first frame period and the second frame period, a thirdphoto-control line may be connected to the third output terminal and thesecond output terminal of the clock driver 620, respectively. A phasedifference between the second clock signal and a third clock signaloutput from the second output terminal and the third output terminal ofthe clock driver 620 may be d2. The arithmetic circuit 640 may calculatea difference between data obtained in the first frame period and dataobtained in the second frame period, such that clock signals output fromthe clock driver 620 through output terminals, for example, a phasedifference between photo-control signals may be calculated.

In an embodiment illustrated in FIGS. 24 and 25, two frame periods maybe required to detect a phase difference error. The two frame periodsfor detecting the phase difference error may be set at the beginning ofan operation in which the image sensor 600 is converted to a wakeupmode, or may be inserted every predetermined period during an operationof the image sensor 600. In an embodiment, by detecting the phasedifference error by allocating two frame periods every predeterminedperiod, it is possible to compensate for a phase difference error changein accordance with a temperature, and a threshold voltage change of thecircuit elements, and to optimize performance of the image sensor 600.

FIG. 26 is a block diagram schematically illustrating an electronicdevice including an image sensor according to an embodiment of thepresent application.

A computer device 1000 according to the embodiment illustrated in FIG.26 may include a display 1010, an image sensor 1020, a memory 1030, aprocessor 1040, a port 1050, and the like. In addition, the computerdevice 1000 may further include a wired/wireless communications unit, apower supply unit, and the like. Among the components illustrated inFIG. 26, the port 1050 may be a device in which the computer device 1000is provided for communicating with a video card, a sound card, a memorycard, a universal serial bus (USB) device, and the like. The computerdevice 1000 may be a concept including a general desktop computer andlaptop computer, as well as a smartphone, a tablet personal computer(PC), and a smart wearable device, and the like.

The processor 1040 may perform specific operations, commands, tasks, andthe like. The processor 1040 may be a central processing unit (CPU) or amicroprocessor unit (MCU), a system on chip (SoC), and the like, and maybe connected to the display 1010, the sensor unit 1020, the memorydevice 1030, as well as other units connected to the port 1050, througha bus 1060.

The memory 1030 may be storage medium for storing data, or multimediadata for operating the computer device 1000. The memory 1030 may includea volatile memory, such as a random access memory (RAM), or anon-volatile memory, such as a flash memory. The memory 1030 may alsoinclude a solid state drive (SSD), a hard disk drive (HDD), or anoptical drive (ODD) as a storage unit. The image sensor 1020 may beemployed in the computer device 1000 in the form of an image sensor inaccordance with various embodiments described with reference to FIGS. 1to 25.

In an embodiment of the present application, an imaging device mayinclude a pixel array having a plurality of pixels, each of which mayinclude a pixel circuit operating at a predetermined timing to generatean electrical signal from electric charge. In an embodiment of thepresent application, performance of an imaging device may be improved bydetecting a phase difference error of a clock signal input to pixelcircuits, and compensating for the phase difference error.

The various and advantageous advantages and effects of the presentapplication may be not limited to the above description, and may be moreeasily understood in the course of describing a specific embodiment ofthe present application.

While the present application has been shown and described withreference to example embodiments thereof, it will be apparent to thoseskilled in the art that modifications and variations could be madethereto without departing from the scope of the present application asdefined by the appended claims.

What is claimed is:
 1. An imaging device comprising: a light sourceconfigured to be operated by a light control signal; and a pixel arraycomprising a plurality of pixels, each of the plurality of pixelsincluding a pixel circuit generating an electrical signal based on anelectric charge, wherein the plurality of pixels comprises a pluralityof general pixels and a plurality of phase difference pixels, whereineach of the plurality of general pixels comprises a photodiode, whereinthe photodiode is configured to generate a first electric charge inresponse to a received optical signal output from the light source andreflected by a subject, wherein the pixel circuit of each of theplurality of general pixels is configured to generate a first electricalsignal based on the first electric charge, and wherein each of theplurality of phase difference detection pixels comprises a switchelement connected to the pixel circuit of each of the plurality of phasedifference detection pixels and an electric charge-supply sourceconnected to the switch element and output a second electric charge,wherein the switch element is configured to be turned on and turned offby a switch control signal, and wherein the pixel circuit of each of theplurality of phase difference detection pixels is configured to generatea second electrical signal based on the second electric charge.
 2. Theimaging device according to claim 1, wherein the pixel circuit comprisesa pixel node configured to receive the first electric charge or thesecond electric charge, wherein one terminal of the switch element isconnected to the second pixel node.
 3. The imaging device according toclaim 1, wherein the plurality of general pixels is disposed in an arrayform in accordance with a row direction and a column direction, andwherein the plurality of phase difference detection pixels is disposedin the row direction.
 4. The imaging device according to claim 3,wherein the plurality of phase difference detection pixels is disposedin a first position in the column direction.
 5. The imaging deviceaccording to claim 3, wherein the plurality of phase differencedetection pixels is disposed in a first position and in a secondposition, and wherein the second position is adjacent to the firstposition in the column direction.
 6. The imaging device according toclaim 3, wherein the plurality of phase difference detection pixels isdisposed in a first position and in a second position separated from thefirst position in the column direction.
 7. The imaging device accordingto claim 1, wherein the plurality of general pixels is disposed in anarray form in accordance with a row direction and a column direction,wherein each of the plurality of phase difference detection pixels isdisposed separately from each other, wherein each of the plurality ofphase difference detection pixels is surrounded by a portion of thegeneral pixels.
 8. The imaging device according to claim 1, wherein theswitch control signal is the same as the light control signal.
 9. Theimaging device according to claim 1, wherein the pixel circuit comprisesa first pixel circuit and a second pixel circuit, and the first pixelcircuit and the second pixel circuit have a same structure, wherein thefirst pixel circuit comprises a first photo transistor configured to becontrolled by a first photo-control signal, and the second pixel circuitcomprises a second photo transistor configured to be controlled by asecond photo-control signal, wherein the second photo-control signal hasa phase difference of 180 degrees from the first photo-control signal,and wherein the imaging device is configured to: input the firstelectric charge or the second electric charge to the first pixel circuitwhen the first photo transistor is turned on, and input the firstelectric charge or the second electric charge to the second pixelcircuit when the second photo transistor is turned on.
 10. The imagingdevice according to claim 9, wherein the switch control signal is thesame as one of the first photo-control signal and the secondphoto-control signal.
 11. The imaging device according to claim 9,wherein the plurality of phase difference detection pixels is disposedin a row direction, wherein the plurality of phase difference detectionpixels comprises a first phase difference detection pixel and a secondphase difference detection pixel adjacent in the row direction, and thefirst phase difference detection pixel and the second phase differencedetection pixel are grouped into one group.
 12. The imaging deviceaccording to claim 11, wherein the switch control signal of the firstphase difference detection pixel and the switch control signal of thesecond phase difference detection pixel are the same as one of the firstphoto-control signal and the second photo-control signal of the firstphase difference detection pixel.
 13. The imaging device according toclaim 11, wherein a portion of the plurality of phase differencedetection pixels is disposed in a first position in a column directionintersecting the row direction, and a remainder of the plurality ofphase difference detection pixels is disposed in a second position,adjacent to the first position in the column direction, and wherein theportion of the plurality of phase difference detection pixels disposedin the first position and the remainder of the plurality of phasedifference detection pixels disposed in the second position are groupedin different manners to each other.
 14. The imaging device according toclaim 9, further comprising: a control logic configured to use dataobtained from the plurality of phase difference detection pixels tocorrect a phase difference error between the first photo-control signaland the second photo-control signal.
 15. The imaging device according toclaim 14, wherein the control logic is configured to use data obtainedfrom the plurality of general pixels to generate a depth map comprisingdistance information between each of the plurality of general pixels andthe subject.
 16. The imaging device according to claim 1, wherein thelight control signal and the switch control signal are pulse widthmodulation (PWM) signals.
 17. The imaging device according to claim 1,wherein the plurality of phase difference detection pixels furthercomprises a light blocking layer blocking the received optical signal.18. An image sensor comprising: a pixel array comprising a plurality ofpixels, wherein at least one of the plurality of pixels comprises afirst pixel circuit having a first photo transistor connected to a pixelnode, a second pixel circuit having a second photo transistor connectedto the pixel node, a switch element connected to the pixel node, and anelectric charge-supplying source connected to the switch element,wherein the first photo transistor comprises a first photogate and thesecond photo transistor comprises a second photogate, and a controllerconfigured to: input a first photo-control signal to the firstphotogate, input a second photo-control signal having a phase differenceof 180 degrees from the first photo-control signal to the secondphotogate, and turn on and turn off the switch element to supply anelectric charge to the pixel node.
 19. The image sensor according toclaim 18, wherein the controller is further configured to: generate alight control signal driving a light source outputting an opticalsignal, and input the light control signal to the switch element as aswitch control signal to turn on and turn off the switch element. 20.The image sensor according to claim 18, wherein the controller inputsone of the first photo-control signal and the second photo-controlsignal to the switch element as a switch control signal to turn on andturn off the switch element.